The invention relates to a device for detectin occupancy for a motor vehicle and, more particularly, to a device for detecting seat occupancy for a motor vehicle, especially for inhibiting airbag release when the seat is unoccupied. The device has a seat occupancy sensor, which is integrated in a seat cushion, and an associated evaluation circuit.
In order to protect vehicle occupants more effectively, motor vehicles, inter alia, are being equipped to an increasing extent with a front seat passenger's airbag. In doing so, no unnecessary damage occurs provided it is possible to release the front seat passenger's airbag in the case of an accident only when the front seat passenger's seat is occupied.
A number of systems for seat occupancy detection are known. Thus, in German Patent document DE-AS 21 25 198, a contact band is integrated into the seat cushion of the motor vehicle seat. Two contact strips of the contact band come into contact when loaded. This contact making is evaluated as a signal for the loading of the seat cushion. The seat occupancy detection can be carried out using contact bands of various patterns, as a result of which locally different sensitivities are achieved.
An embodiment for seat occupancy detection, which furthermore allows locally resolved evaluation of the load, is known from U.S. 5,010,774. In this reference, a matrix of pressure-sensitive contact points is evaluated in order to detect the load on the backrest of a seat by a trial person as a function of different designs of the seat. Furthermore a trial shoe is known from the document, having a pressure-sensitive bottom, in the case of which the pressure load on the running sole and the step can be separately evaluated.
In German Patent document DE 42 37 072 C1, a sensor mat is described for installation in the seat cushion of a motor vehicle seat. The sensor mat is constructed as a resistive membrane pressure sensor and, in addition to interrogation of the seat occupancy status, also allows simple interrogation of the functional status, i.e., a self check.
The known systems for detecting seat occupancy signal the seat occupancy independently of the sitting position of the occupant. As a result, airbag release is also allowed independently of the sitting position. However, it is advantageous for an optimum impact-damping effect of the airbag if a minimum distance is ensured between the occupant and the airbag at the start of the airbag release, in order for there to be sufficient time for the airbag to unfold in the case of an accident.
There is therefore needed a system for detecting seat occupancy such that an incorrect sitting position (out of position) close to the front seat edge, in the case of which the minimum distance mentioned above is not maintained, can be detected and the occupant warned.
This need is met by a device for detecting seat occupancy for a motor vehicle and, more particularly, to a device for detecting seat occupancy for a motor vehicle, especially for inhibiting airbag release when the seat is unoccupied. The device has a seat occupancy sensor, which is integrated in a seat cushion, and an associated evaluation circuit. The seat occupancy sensor is divided into a front sensing region and a rear sensing region. The front sensing region responds to seat occupancy in the front region of the seat cushion and the rear sensing region responds to seat occupancy in the rear region of the seat cushion. It is possible to evaluate the occupancy state of both sensing regions separately. By splitting the sensitive region of the seat occupancy sensor into a front sensing region and a rear sensing region, a sitting position close to the front seat edge can be detected and an appropriate warning signal emitted.
This measure makes particular sense if, despite the warnings in the operating instructions from the vehicle manufacturer, children are seated on the front seat without there being a suitable child restraint system. Because of their shorter thighs, small children prefer to sit on the front seat surface for added comfort. Using the device according to the invention for seat occupancy detection, in conjunction with an audible or visual warning device, the driver can be emphatically advised to ensure that the front seat passenger is in a correct sitting position.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.